1. Field of the Invention
The present invention generally relates to heater control methods and storage apparatuses, and more particularly to a heater control method for controlling a built-in or integrated heater of a head, and a storage apparatus that is provided with a head having a built-in or integrated heater controlled by such a heater control method.
2. Description of the Related Art
A head used in a storage apparatus such as a conventional hard disk drive (HDD) is deformed depending on a temperature change, and for this reason, an error rate changes due to the effects of the head deformation. The temperature change includes a temperature change caused by an environment in which the head is used, and a temperature change caused by the heat that is generated by the head itself.
Particularly in the case of a head which has a relatively low temperature at an initial stage of a write operation, the head is deformed by the heat that is generated by the head itself when the write operation is carried out, and a gap between the head and a recording medium such as a disk medium changes. For this reason, the error rate is poor at the initial stage of the write operation because the gap between the head and the disk medium is large and the write ability (or capability) is poor, but the gap between the head and the disk medium decreases with the lapse of time and the write ability improves to thereby improve the error rate. As a result, when designing the HDD, it is difficult to set the gap between the head and the disk medium to an optimum value suited for high-density recording, and in addition, it is difficult to greatly improve the yield of the HDD.
Recently, a technique has been developed which provides a heater within the head, and controls the heater by a heater driving circuit to control the heat generated by the head, so as to control the deformation of the head in use. By controlling the head deformation, that is, a projecting amount of the head with respect to the disk medium, it is possible to control the gap between the head and the disk medium. Such a technique is proposed in a Japanese Laid-Open Patent Application No. 2004-13931, a Japanese Laid-Open Patent Application No. 2004-342151, and a U.S. patent application publication No. US2005/0057841A1.
FIG. 1 is a time chart for explaining heater ON/OFF timings of the prior art corresponding to the U.S. patent application publication No. US2005/0057841A1. In FIG. 1, SDEN denotes a control signal for controlling ON/OFF states of the heater, *R/W-I denotes a signal indicating a read/write command processing time (low active), and Heater denotes a signal indicating a heater ON/OFF time. As may be seen from FIG. 1, after the ON-value of the control signal SDEN is set in a register and the heater is turned ON via a serial interface, the heater is maintained in the ON state until the OFF-value of the control signal SDEN is set in the register and the heater is turned OFF via the serial interface, even if a target write interval in which the heater is to be turned ON ends. In other words, although the heater does not need to be maintained in the ON state during the read command processing time after the write command processing time, the heater is maintained in the ON state to thereby consume unnecessary power.
When driving the head having the built-in heater, the power consumption increases compared to the case where no built-in heater is provided in the head. However, the prior art controls the ON/OFF states of the heater via the serial interface, and there is a problem in that it is difficult to reduce the power consumption because the heater is driven even at times that are actually unnecessary.